Epigenetics News

Epigenetics: DNA modifications “more diverse than thought”

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From ScienceDaily:

The world of epigenetics — where molecular ‘switches’ attached to DNA turn genes on and off — has just got bigger with the discovery by a team of scientists from the University of Cambridge of a new type of epigenetic modification.

Epigenetics has so far focused mainly on studying proteins called histones that bind to DNA. Such histones can be modified, which can result in genes being switched on or of. In addition to histone modifications, genes are also known to be regulated by a form of epigenetic modification that directly affects one base of the DNA, namely the base C. More than 60 years ago, scientists discovered that C can be modified directly through a process known as methylation, whereby small molecules of carbon and hydrogen attach to this base and act like switches to turn genes on and off, or to ‘dim’ their activity. Around 75 million (one in ten) of the Cs in the human genome are methylated.

Now, researchers at the Wellcome Trust-Cancer Research UK Gurdon Institute and the Medical Research Council Cancer Unit at the University of Cambridge have identified and characterised a new form of direct modification — methylation of the base A — in several species, including frogs, mouse and humans.

“It’s possible that we struck lucky with this modifier,” says Dr Koziol, “but we believe it is more likely that there are many more modifications that directly regulate our DNA. This could open up the field of epigenetics.” More.

See also: Epigenetic change: Lamarck, wake up, you’re wanted
in the conference room!

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Note: Add “more diverse than thought” category to the list that includes “more complex than thought,” and “earlier than thought”

File:Epigenetic mechanisms.jpg
Epigenetic mechanisms/NIH

Here’s the abstract:

Methylation of cytosine deoxynucleotides generates 5-methylcytosine (m5dC), a well-established epigenetic mark. However, in higher eukaryotes much less is known about modifications affecting other deoxynucleotides. Here, we report the detection of N6-methyldeoxyadenosine (m6dA) in vertebrate DNA, specifically in Xenopus laevis but also in other species including mouse and human. Our methylome analysis reveals that m6dA is widely distributed across the eukaryotic genome and is present in different cell types but is commonly depleted from gene exons. Thus, direct DNA modifications might be more widespread than previously thought. (paywall) – Magdalena J Koziol, Charles R Bradshaw, George E Allen, Ana S H Costa, Christian Frezza, John B Gurdon. Identification of methylated deoxyadenosines in vertebrates reveals diversity in DNA modifications. Nature Structural & Molecular Biology, 2015; DOI: 10.1038/nsmb.3145

One Reply to “Epigenetics: DNA modifications “more diverse than thought”

  1. 1
    bornagain says:

    Of related note:

    Ask an Embryologist: Genomic Mosaicism – Jonathan Wells – February 23, 2015
    Excerpt: humans have a “few thousand” different cell types. Here is my simple question: Does the DNA sequence in one cell type differ from the sequence in another cell type in the same person?,,,
    The simple answer is: We now know that there is considerable variation in DNA sequences among tissues, and even among cells in the same tissue. It’s called genomic mosaicism.
    In the early days of developmental genetics, some people thought that parts of the embryo became different from each other because they acquired different pieces of the DNA from the fertilized egg. That theory was abandoned,,,
    ,,,(then) “genomic equivalence” — the idea that all the cells of an organism (with a few exceptions, such as cells of the immune system) contain the same DNA — became the accepted view.
    I taught genomic equivalence for many years. A few years ago, however, everything changed. With the development of more sophisticated techniques and the sampling of more tissues and cells, it became clear that genetic mosaicism is common.
    I now know as an embryologist,,,Tissues and cells, as they differentiate, modify their DNA to suit their needs. It’s the organism controlling the DNA, not the DNA controlling the organism.
    http://www.evolutionnews.org/2.....93851.html

    Body Plans Are Not Mapped-Out by the DNA – Jonathan Wells – video
    http://www.youtube.com/watch?v=meR8Hk5q_EM

    Podcast – Richard Sternberg PhD – On Human Origins: Is Our Genome Full of Junk DNA? Part 5
    (emphasis on ENCODE findings and the loss of the term ‘gene’ as an accurate description in biology and also how that loss undermines the modern synthesis of neo-Darwinism)
    http://www.discovery.org/multi.....-dna-pt-5/

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